1. Field of the Invention
The present invention relates to a boundary radiation prevention structure. In particular, the present invention relates to a boundary radiation prevention structure for blocking and absorbing the electromagnetic wave radiating to protect the system from interferences.
2. Description of the Related Art
Nowadays technology of RFID (Radio Frequency Identification) has a fruitful development. Because of its appropriate acting distance, affordable cost, small volume, enduring life cycle, and free of battery, RFID is widely used in a variety of fields. For example, it can be applied in as the following fields: labels in supermarket, plastic money for debit and stored-value, electronic key, book position searching in the library and the like.
When applying the RFID, at least one RFID tag attached to an object or a stock keeping unit (SKU) to record information and at least one antenna for detecting the MID tag are needed. The antenna is electrically connected (such as using RF coaxial cable) to the RFID reader so that transmitting and receiving of signals are achieved. Each of the objects or SKUs is matched with an RFID tag, and the system gets the information of the objects or SKUs (called “object information” for short) automatically via detecting their RFID tags. When the RFID technology is applied in searching location of specific objects, practically a control system connected to at least one RFID reader is needed. The reader connects to multiple antennas which are placed in different locations so that it can detect the locations of the objects with their correspondent RFID tags.
However, due to the electromagnetic wave radiation, if the regions for placing objects are too close to each other, the electromagnetic waves from the reader and tags are easily to spill to other regions when a traditional compartment is used. Therefore, one RFID reader antenna detects the signals from the RFID tags locating not only in the antenna predefined region but also in the other nearby regions, leading to an error position determination, so that the control system is unable to determine the position of the object corresponding to the RFID tag correctly.
Among such shortcomings, applying to the cabinet for placing objects is more annoying. Taiwan Patent Number M379122 discloses a remote-controlled electronic bookshelf device, comprising at least one bookcase and a remote control host, wherein an RFID reader is in each bookcase, and each book in the bookcase is attached with an RFID tag having an unique identifier. The remote control host is separated to the bookcases and is connected to the RFD reader. A database of all identifiers of books is stored in the remote control host, and another RFID reader is used for reading the identifier of the MID tag so that remote control of borrowing and returning books is achieved. However, electromagnetic wave in this kind of bookcase will spill out to another region by radiation and the signals of RFID tags would interfere to each other so that the RFID reader cannot identify the location of books correctly, and the electronic bookshelf cannot perform the book locating function properly.
FIG. 1 and FIG. 2 are schematic diagrams of electronic bookshelf. In order to avoid the electromagnetic wave 400 across two compartments 200 causing signal interference, a metal plane 300 is set between the two compartments 200 as a shielding and the metal plane 300 can prevent the electromagnetic wave 400 from spill over to adjacent compartment 200. Therefore, the antenna 13 in each compartment 200 can read the object information correctly. However, when the electromagnetic wave 400 radiates to the metal plane 300, it induces an induced current on the surface of the metal plane 300. When the induced current passes to the edge of metal plane 310, it emits a boundary radiation 500 from the edge of the metal plane 300. Therefore, the RFID reader antenna might detect the signals of tags from other compartment via boundary radiation 500.